The Ultimate Guide To Master Astrophotography (Part 2)


If you missed part one find it here.

 

Camera and Lens Systems.

 

Modern digital single-lens reflex (DSLR) cameras are truly masterpieces of technological innovation. Steadily improving year after year, today’s DSLRs boast powerful sensors, sophisticated controls, and reliable performance at modest cost. The best news is that even entry level DSLRs today are easily capable of capturing the faint glow of the Milky Way, star trails, and the other nightscape images described in this guide.

 

The discussion on cameras in this guide is confined to those with digital sensors, since they have largely replaced film in landscape astrophotography. This section will review the essential features of DSLRs that are the most important in landscape astrophotography. We will review characteristics of camera sensors, focus and metering modes, lens characteristics and selection, and factors that govern image sharpness.

 

 

Astrophotography

 

 

Camera Sensor.

 

The camera sensor is the heart of every imaging system. It is your camera’s retina. The sensor is responsible for converting the image that the lens produces into electrical signals that are digitally analyzed and stored on memory devices. The sensor is a semiconductor device that has been processed so that its surface contains millions of individual pixels. Each pixel is a tiny optoelectronic device, often measuring only a few micrometers in dimension.

 

Pixels are either etched out of the original silicon wafer, built up with the deposition of additional layers of photosensitive and electronic materials, or both.

 

Incoming light is converted into electrical signals by each pixel in an analogous manner that the rods and cones in your eye’s retina convert incoming light to biochemical signals. Furthermore, sensors contain red, green, and blue pixels, just like the red, green, and blue cones in your retina. The incident light upon each pixel is converted into an electrical signal representing the strength of the particular hue of light that the particular pixel received.

 

By examining the relative values of the signals from immediately adjacent red, green, and blue pixels, the actual color of light incident upon the pixels, or its hue, can be reproduced in the same way the light would be perceived by a human retina. The intensity of the light is determined by the absolute magnitude of the signals from each of the pixels.

 

The pixels in the sensors are optoelectronic devices. As such, they are inevitably susceptible to intermittent variations and false positives. Sometimes, they randomly indicate the presence of light when there is none. Other times, a high energy photon or other cosmic ray may trigger an event that the pixel records as light. In yet other instances, separate measurements of the same light levels can yield slightly different results. In such cases, these artifacts are collectively known as noise, and are an undesirable, yet unavoidable consequence of digital imaging.

 

The goal in imaging is to maximize the signal to noise ratio, or to limit the noise to a level that is so low that it is unnoticeable. Sensors are characterized by several parameters, including the number of pixels they contain, their physical dimensions, and their signal-to-noise ratio. The number of pixels can be a very misleading parameter by itself, since small sensors can still contain a relatively large number of extremely small pixels.

 

While such sensors can produce acceptable photographs under bright light conditions, they are prone to very noisy performance in low light conditions, and are typically unsuitable for significant enlargements. These sensors typically find their way into consumer electronics such as cell phones and security cameras where noise at low light levels is tolerable, and the need for enlargements rare. DSLRs with larger sensors that contain a high number of relatively large pixels are best suited for landscape astrophotography.

 

Such sensors are typically referred to as full–frame, compared to crop sensors, which are roughly two-thirds the size of full-frame sensors. Large, full-frame sensors generally have very good low-light performance with much less noise than smaller sensors with smaller pixels. The best way to evaluate a sensor for landscape astrophotography, other than by price, is by examining its noise levels in images created in low light conditions at high ISO settings, characterizations that are frequently available online.

 

 

Helpful Camera Features for Landscape Astrophotography.

 

There are several helpful and even critical camera features for landscape astrophotography. The most important is the ability to create exposures using manually controlled settings. Specifically, you need to be able to independently set the ISO, aperture, and shutter speed.

 

The second most important capability is the ability to manually focus the lens, which you will find yourself doing every night. Productive nightscape sessions are virtually impossible without these two vital camera features. Having the ability to create quality images at the relatively high ISO settings of 3200, 6400, and even 12,800 is also helpful. Although such high ISOs are rarely used in other environments, they can be extremely valuable in landscape astrophotography. For example, you may find it helpful to create high ISO images of the night sky to blend in with low-ISO images of interesting foreground subjects.

 

 

File Format.

 

It is a near certainty that the DSLR you will use for landscape astrophotography will allow you to record your images in either a JPEG or RAW file format. I strongly urge you to consider the benefits of always using a RAW file format for your images henceforth, whether or not you also save a second copy in a JPEG format.

 

The fundamental difference between these two file formats is in image quality. Images created in a RAW file format contain the maximum possible image information. The signal from each RGB channel of each pixel is separately measured and saved.

 

In contrast, the vastly smaller size of JPEG files is achieved through significant averaging of values from adjacent pixels with similar signals, in other words, file compression. Unfortunately, file compression irreversibly deletes sometimes-valuable information through its process of averaging. While cumbersome and bulky, the extra size of RAW files provides the maximum latitude for post-processing of images.

 

 

Lens focal length.

 

There are a few key lenses that you will want to include in your landscape astrophotography arsenal. Each one has specific features that make it advantageous for specific instances.

 

Lenses are characterized mainly by their focal length, f. The focal length is the distance between the center of the lens and the focal point for parallel incoming rays of light, F. It is an inherent property of the lens. The focal length should not be confused with the subject focus distance, o, which is the distance between the center of the lens and the subject. The focus distance changes with each subject, and can range from a few inches to infinity, whereas the focal length is a fixed property of the lens and never changes.

 

Put another way, three lenses with focal lengths of 16 mm, 50 mm and 200 mm, respectively, can all have the same subject focus distance of 35 feet for a subject 35 feet away from the center of the lens, even though their focal lengths are all different.

 

 

Field of View.

 

The focal length is an extremely important parameter. It controls many other key lens characteristics, including its field of view (FOV). The FOV is the angle between lines connecting the camera to opposite sides of the image. Telephoto lenses have a very narrow FOV of only a few degrees, while wideangle lenses can have FOVs well over 100°. In addition to influencing the overall feel of your composition, the FOV can be very important in planning the basic feasibility of a given nightscape project.

 

For example, knowing the FOV of your lens can help determine whether or not a certain combination of constellations will fit into a single image created by that lens, or whether the North Star will fit into the same image as the horizon during a star trail composition.

 

 

Aperture.

 

The maximum possible aperture, or the smallest f-stop, of the lens is another key lens criterion. The f-stop is calculated by dividing the focal length of the lens, f, by the diameter of the aperture, D. For example, a lens with a focal length of 100 mm and an aperture set to a physical dimension of 25 mm will thus have a f-stop of 100 mm/25 mm = f/4.

 

The reason behind the nomenclature of the f-stop, f/, is now clear; the diameter of the aperture is defined as focal length, f, divided by, or “/”, the f-stop number. Thus: f/! You can also now appreciate why lenses that have a smaller minimum f-stop are so much more expensive; they simply use more glass that must be shaped and polished to optical perfection over a larger lens potential opening.

 

To see an example of this difference, let’s consider two 35 mm lenses, one with a minimum f-stop of 1.4 and the other with a minimum f-stop of 4.5, such as those commonly sold as a kit lens with entry-level DSLRs. For the first lens, the maximum aperture (minimum f-stop) is 35 mm/1.4 = 25 mm, or approximately one inch. For the second lens, the maximum aperture is 35 mm/4.5 = 7.8 mm, or only about one-third of an inch. The second lens, therefore, uses much less glass and thus is inherently cheaper and less demanding to manufacture.

 

Subject Distance.

 

When choosing a lens and subject distance combination for landscape astrophotography, one important issue that bears consideration is the size of your foreground subject within your composition.

 

 

Image Sharpness.

 

The aperture setting affects the resultant image’s overall sharpness and quality, even when in perfect focus. There are two competing phenomena that cause this result: lens imperfections at minimum aperture and diffraction at maximum aperture.

 

When the aperture is wide open, i.e. at its minimum value, light passes through nearly the entire body of the lens to reach the sensor. In contrast, when the aperture is set to higher values, for example f/8, or f/11, we say that the lens is “stopped down” and the physical size of the aperture is smaller. The aperture now blocks incoming light from the periphery of the lens, so that only light that impinges upon the central region of the lens is able to pass into the camera.

 

The front surface of any lens at its periphery is naturally more curved than its center, which is nearly flat. A number of unavoidable lens imperfections, specifically, spherical aberrations, chromatic aberrations, and coma become important as the result of the greater lens curvature accessed at minimum aperture.

 

Spherical aberration causes a noticeable softening of the focus in the image. It results from the inability of light from the entire front surface of the lens to converge precisely at a single point within the image.

 

Chromatic aberration is an optical phenomenon with its origins in the wavelength-dependent refractive index of optical glass. Images exhibiting chromatic aberration exhibit noticeable colored fringes surrounding bright objects, such as stars. Coma is the result of light sources, such as stars, that are located around the periphery of the images failing to focus in a single point but rather in a flareshaped area at minimum aperture, and has its origins in the spherical aberration described above.

 

Finally, lens vignetting becomes more pronounced at minimum aperture since off-axis light travels through more glass and decreases in intensity, coupled with the tendency of the lens housing to partially block light entering near the lens periphery. Even the very best lenses exhibit these various effects at minimum aperture, although their effects are far more pronounced at the lowest minimum apertures, e.g. f/1.4 or f/2.0. In contrast, at the very minimum aperture dimension, i.e. maximum f-stop (e.g. f/22), the aperture diagram is now reduced to a narrow restriction. In this case, optical diffraction occurs around the edges of the diaphragm blades, producing noticeable softening of the image focus.

 

Although diffraction occurs at any aperture setting, its effects become minimized by the relative abundance of light from the bulk of the lens far from the diaphragm blades at wider apertures.

 

 

Focusing.

 

Learning how to achieve a good focus in the dark, whether it is on the stars, or on foreground subject, is probably the most difficult challenge to confront landscape astrophotographers. It is very important to learn how to achieve and confirm the best focus possible. While the compressed JPEG image on your camera’s rear screen may look perfectly acceptable, examination at full scale on a monitor may reveal an image with visibly out-of-focus stars.

 

 

Optics of Focus.

 

Nightscapes are appealing precisely because of their in-focus foreground coupled with an in-focus night sky. Foreground objects can be out of focus if they are too close to the camera when the lens is focused on the sky. This section describes the two main approaches to reliably achieving sharp focus across the entire image—what to set and what to guard against.

 

In order to understand the camera and lens settings that control the near focus distance, let’s introduce a few parameters needed to describe the physics behind the optics of focus. We’ve already introduced the object focus distance, o, and the lens focal length, f. The depth of field (DOF) is the distance between the far and near focus points, bf, and bn. Second, we will assume the night sky lies at an infinite distance from the camera. Finally, we need to introduce the term, circle of confusion (CoC). The CoC is simply the size, or diameter, of the smallest circle that is resolvable by your camera’s sensor.

 

Put another way, if a distance corresponding to the CoC separates two tiny dots of light on your sensor, they are distinguishable as two separate dots. If they are moved any closer together, they blend into a single dot. You may like to think of the CoC as the resolution limit of your camera’s sensor. It is roughly equivalent to the pixel dimension, or alternatively, as the approximate size of the rod and cone cells in your eye’s retina. Consequently, it makes sense that if two tiny dots of light are incident on a single cone cell, there is no way for that cell to know if there are two dots of light, one dot of brighter light, or even eighteen dots of dimmer light! In contrast, if the two dots of light are placed on two separate cells, then they are easily distinguishable.

 

Objects appear in focus if each point within them is focused to a spot smaller than the CoC, since they can then be distinguished by separate pixels. They appear blurred, or out-of-focus if their focused spot is larger than the CoC, and thus spread over more than a single pixel.

 

Consequently, the DOF is determined simply by the distance between the closest, and farthest away objects whose images are focused to spots smaller than the CoC. The first approach to achieving sharp focus across the entire image is to focus directly on a star, a planet, or the moon. These objects are effectively at a subject distance of infinity. The next step is to look up the near focus distance for the relevant combination of lens focal length and aperture setting. Being sure that all the foreground elements within your composition are further away from the camera than this distance will ensure that they remain in focus while your camera is focused on the sky.

 

Wide-Angle Lenses—14–24 mm.

 

Wide-angle lenses in the 14–24 mm focal length range are favorites of most landscape astrophotographers. Without the major distortion of the fisheye lens, wide-angle lenses can simultaneously capture wide swaths of the night sky and relatively undistorted foreground subjects in a single image.

 

They excel at capturing sunsets and sunrises; Milky Way images, star trails, meteor showers, and nightscapes of the aurora. Images involving the rising or setting of the full moon, however, are best shot with longer focal length lenses, since the moon becomes lost in such a wide FOV. Lenses in this focal length range are available as either prime or zoom lenses. They are also available with a range of apertures, some as low as f/1.4. Depending on your budget, these lenses are excellent investments, and rarely fail to satisfy.

 

24–70 mm Focal Length.

 

Owing to their more restricted FOV, lenses in the 24–70 mm range tend to be chosen when specific night sky objects make up the essence of the composition. They make excellent choices for nightscapes involving the rising and setting of the full moon, star trails, and images including the galactic core of the Milky Way. They are also valuable when photographing local regions of the aurora. Finally, they are perfect for creating images used for panoramas.

 

Another advantage of lenses in this focal length range is that they are widely available as prime lenses with very low minimum aperture, some as low as f/1.2. The fully manual versions of these wide aperture lenses are also quite inexpensive and are very well worth considering since you will rarely be using auto focus during your night sky forays. Combining two or more images from such lenses in a panorama can offset the substantial coma distortions that occur at the lowest aperture settings. The central, sharpest regions are preserved, along with the extraordinary light-capturing ability of these lenses. Greater than 70 mm Lenses with a focal length above 70 mm are relatively uncommon in landscape astrophotography.

 

 

One reason is that many night sky objects are simply too large to fit into their relatively restricted FOV. Another reason is that relatively short exposure times are necessary to avoid significant streaking or trailing of stars. One area where these focal length lenses excel, however, is in creating nightscapes involving the rising and setting of the full moon. In such compositions, the requisite relatively short exposure times coupled with the need to isolate the area of the full moon rising or setting are both perfectly satisfied by lenses with relatively long focal lengths.

 

 

Exposure.

 

Knowledgeable exposure is the core skill of quality photography. Achieving the right combination of light and shadow that matches, or even amplifies, your artistic vision is the essence of success. In this section, we will focus on what you need to know about photographic exposure to truly master landscape astrophotography.

 

Camera Exposure Value, EV, and Matching EV to LV.

 

The primary photographic challenge, especially in landscape astrophotography, is to collect the right amount of light to produce a properly exposed image, regardless of the amount of light originating from the scene. Historically, a “properly exposed” image is one with an overall brightness that is 18 percent gray, or 18 percent of the way between black and white.

 

When we view scenes with differing light values with our eyes, our vision system handles this light collection and conversion process automatically; for example, our irises dilate/contract and our retinas become more or less sensitive. In photography, however, this process is done by the photographer, and is accomplished by setting the exposure value (EV) of the camera to correspond to the light value (LV) of the scene. The EV depends mathematically on the ISO, I, aperture, A, and shutter speed, T, according to the logarithmic relationship: EV = log2 ( ).

 

To summarize, when we match the camera EV to the scene LV, we are assured of obtaining a correctly exposed image, i.e. one that is on average 18 percent gray, even if the subject scene is extremely dark or bright. The overall brightness of the resultant image will be the same.

 

Now, in practical terms, rarely, if ever, will you need (or want) to actually calculate your camera’s numerical EV, since your camera’s built-in light meter and analysis system does all the work for you. Instead, by taking a light meter reading of the scene of interest, you will be shown whether your current combination of ISO, aperture, and shutter speed is suitable to match the scene LV, or if it is too high or too low and you might wish to make adjustments. However, your understanding of:

 

(a) the LV levels of typical landscape astrophotography scenes and.
(b) what combinations of ISO, aperture, and shutter speed are available to match them.

 

will be of enormous value in planning and avoiding a frustrating night of trial-and-error in the field while your subjects slowly slip below the horizon in front of your eyes! By way of example, imagine that we want to create a nightscape image with the Milky Way on a moonless night. We know that scenes such as these typically have an LV in the range of approximately −8 to −5.  Therefore, we know that in order to match this light value to obtain a properly exposed image, we should set our camera to a corresponding EV of approximately −5. If our camera’s EV setting is set to correspond to a much dimmer LV, for example −12, the resultant image will be too bright.

 

This is because the camera is set to receive less light than it actually would receive, like walking around in daylight with dilated pupils. On the other hand, if the camera’s EV setting is too high, say −2, then the resultant image will be too dark. In this case, the camera requires more light than is available for a properly exposed image.

 

 

Aperture.

 

In the vast majority of cases, you will want to set as low an aperture number, or f-stop, as is feasible. Notice I did not say as low as possible but feasible. There is an important difference. A low f-stop corresponds to an aperture that is physically large or wide open. So why not simply set the aperture to its minimum value, for example, f/2.8 or even f/1.4 to allow as much of the ambient light from the scene into our cameras as possible? You will recall that one reason is that an aperture set to its minimum value can allow lens imperfection effects, especially apparent in astrophotography.

 

 

Aperture

 

 

Also, images made at minimum aperture can appear noticeably softer, which, for example, can impact the appearance, or crispness, of the Milky Way.

 

 

 

 

Consequently, the best compromise between coma and a too-restricted aperture is generally to set your aperture to one to two stops above the minimum aperture of the lens: for a lens with a minimum aperture of f/2.8, that would be f/5.6; for one with a minimum aperture of f/4, that would be f/8.

 

 

Shutter Speed.

 

The only real limitation on shutter speed, or exposure duration, in most landscape astrophotography images relates to undesirable effects of moving subjects. Distracting artifacts can manifest themselves as either unwanted streaking/trailing of stars or blurred foreground objects resulting from wind or other motion. In either case, keeping the shutter speed below a certain value will eliminate the appearance of movement. However, owing to restrictions on aperture such as coma, it may be necessary to keep the shutter open long enough to obtain a correct exposure.

 

So, how long a shutter speed is too long? For years, the practical “Rule of 400/500/600” has been the go-to guide for estimating the maximum exposure length that can be implemented without noticeable star trails. The idea is simple; just divide the number 400, 500, or 600 by the focal length of the lens (in millimeters) to obtain the maximum shutter speed (in seconds) that may be safely used. Using the number 400 gives the most conservative estimate and is my recommendation for those with higher resolution cameras; using the number 600 may suffice for less critical audiences.

 

Note: for users with crop sensor cameras, you will need to multiply the lens focal length by the crop factor (generally 1.5 or 1.6) to arrive at the correct focal length to use in the Rule of 400/500/600.

 

 

ISO.

 

The ISO setting refers to the overall sensitivity of the camera sensor to light, and dictates how much light is needed to obtain a properly exposed image, or one that has an overall gray level of 18 percent. So why not simply set the ISO to the maximum possible setting? Images made with a low ISO setting need lots of light.

 

 

iso

 

The results are images with very high resolution, in other words, images that can be enlarged without losing detail or revealing pixel noise or grain.

 

In contrast, images made with high ISO generally suffer from distracting graininess and often visible color noise. Why is this the case? Think of it as if you were making a painting made up of individual dots of paint. With high ISO images, you’re only allowed to use, say, 1,000 individual drops of paint to make up your painting, and so you have to use a fairly coarse brush.

 

With a low ISO image, you would need 1,000,000,000 drops of paint and thus you are able to use an exceeding fine brush capable of exquisite detail. Herein lies the origin of the higher inherent quality of low ISO images, and their ability to be enlarged significantly without a loss of detail. Finally, images made at higher ISO settings exhibit less dynamic range and less color contrast, and have less capability for significant adjustments during post-processing.

 

Selecting ISO, Aperture, and Shutter Speed for Optimum Image Quality.

 

It’s time to synthesize this knowledge into a cohesive strategy for producing the best possible landscape astrophotography image given the local conditions. Here are the key points so far:

 

Matching camera EV to scene LV is the priority for a correctly exposed image
Low ISO is better than high ISO, to minimize graininess and color noise
The shorter the shutter speed the better, to minimize star trailing and foreground blur
Best aperture is two stops above the minimum, to produce distortion-free images

 

We are now prepared to see how this knowledge is applied in the field. Since we know what settings produce the highest quality images, why not just set the ISO to its lowest value, say, ISO = 100, set the aperture two stops above the minimum, say f/5.6 for a lens with a minimum aperture of f/2.8, and the shutter speed of the longest value needed to avoid star trailing, say 30 seconds for a 20 mm lens?

 

These settings result in a camera EV of EV = 0. Unfortunately, a great many landscape astrophotography scenes have much, much dimmer LVs, such as LV = −6 for scenes involving the Milky Way on moonless nights. This is a very significant difference; a camera set to an EV of 0 will unacceptably underexpose such a scene and will not work.

 

Consequently, we enter the arena of intentional trade-offs in camera settings. Suppose we bump up the ISO – how far can we go before the graininess is noticeable? How about the aperture – can we open it up more without terrible effects? And so on.

 

Once you have experienced this process a few times under night sky conditions, you will develop your own set of references to refine and return to time after time. Remember, the goal is to maximize the time in the field acquiring images and minimizing the amount of time adjusting the exposure settings!

 

 

Developing your astrophotography session plan.

 

This section helps you develop a detailed plan for your nightscape session based on your understanding of astronomy and photography. It includes a predetermination of your shooting location, a detailed schedule and suggested camera settings, along with the appropriate lenses and any specialized equipment that you might need for all your shots.

 

Sounds good, right? Spending the time beforehand to clearly think through your objectives will help you stay on track when you are in the field. It will allow you to concentrate on the creative aspects of your session instead of getting bogged down in technical details and distractions that could have been minimized or avoided altogether. Having a plan will make the difference between being unpleasantly surprised by the unexpected appearance, or lack thereof, of a crucial night sky object; or enjoying the confirmation of observing an anticipated sequence of astronomical events unfolding on schedule before your eyes. There are six main steps:

 

(1) developing the concept;
(2) choosing the shooting location and date;
(c) choosing the shooting time;
(d) selecting the appropriate lens and appropriate exposure settings, and,
(e) summarizing your plans and timeline for the session.

 

It’s easier than it sounds! The main reason for laying out each of these steps explicitly is to make sure we don’t overlook anything. Also, this structure helps provide a logical sequence to the many decisions that you may wish to make. We will now go through each step in detail.

 

Pre-Visualization and Developing the Concept.

 

Begin your planning process with a specific concept in mind; be it star trails, an image of the Milky Way, a meteor shower, or perhaps the full moon rising.

 

Better yet, pre-visualize your nightscape image—close your eyes and think carefully about the image you’d like to create. Be as detailed as possible; is there a specific foreground subject in your image like a particular mountain peak or a well-known rock arch; or more general subjects like patches of wildflowers or a lake with a fishing pier? How are the night sky objects positioned relative to the foreground; does the Milky Way appear to rise directly upwards out of a river or waterfall; or does it arch horizontally across the sky?

 

If you are creating star trails, how exactly are they oriented relative to the horizon—do they angle upwards, curve across the horizon, or form complete circles? How well illuminated is the foreground; are you looking for dark silhouettes, or is a well-lit foreground important? Is the moon rising over, or next to some historic or natural landmark?

 

While it may sound obvious, pre-visualizing your images gives you the answers needed to narrow down your choices of dates, times, locations, lens choices, camera setting, and exposure strategies to those that will practically guarantee that you’ll return home with memory cards chock full of exciting images! Having a pre-visualized scene in mind also helps enormously as you scout your destination during both the day and at night.

 

I have experienced déjà vu many times as I’ve come across scenes that uncannily match their pre-visualized version; the process of pre-visualization can help in “knowing” when you’ve arrived at a good spot. Also, it is always surprising how many unexpected distractions develop in the field to pry your attention away from the subtleties of composition.

 

For example, mosquitoes, thick brush, ticks, incipient clouds, incipient moonrise, cold, wind, difficulty in achieving focus, lights from other people, dying batteries, dehydration, not getting lost and even sleepiness can all interfere with the creative process of landscape astrophotography. Having a well thought out, pre-visualized image in mind, with all the critical elements clearly identified, helps keep you on track.

 

Choosing azimuth and altitude of the night sky subject.

 

The next phase of planning involves identifying the general compass direction, or azimuth of your night sky subject on the selected dates, along with its height above the horizon, or its altitude, measured in degree.

 

While you may recall correctly that the azimuth and altitude of night sky objects change during the night, we only need to assess their general range at this stage. You may obtain the azimuth and altitude of your night sky subjects at various times on your candidate dates with the help of the star charts, planispheres, and planetarium. Monthly publications of star charts are available online, and also appear in magazines such as Astronomy or Sky & Telescope. Several useful apps and programs are also available such as Distant Suns, Star Walk, Stellarium, and Google Sky.

 

 

Choosing the Location.

 

We can now explore a few locations where we might set up our equipment for the night, provided a suitable foreground subject is available. Start with a location with the darkest possible skies, free from cities and other sources of light pollution. Even if your general destination is dictated by other constraints, it is worthwhile driving a short distance if it can help alleviate light pollution levels.

 

 

Choosing Lens and Camera Settings.

 

The last stage of preparation before we summarize our overall plan is to select the appropriate lens and exposure settings. Lens selection can be done with reference to the lens field of view (FOV. Namely, you will want to select the appropriate lens needed to create your pre-visualized image based upon the azimuth and altitude requirements of your night sky subject(s) as well as the necessary FOV needed to include your foreground.

 

For example, if you wish to create a star trails image with trails encircling the North Star with land-based foreground objects also visible, then the angular FOV of the lens must be wide enough to exceed the angular position of the North Star above the horizon, which you may recall is approximately equal to your latitude. Alternatively, if you wish to create a Milky Way image, you will want to select a lens with a narrower FOV; e.g. one with a focal length of 35 mm or greater. Finally, if you wish to create an image containing a specific range of constellations, for example, Sagittarius and Scorpius, then you’ll need to match the FOV of your lens to the required FOV of the constellations, which can be obtained from the simulation apps.

 

Choosing and mounting the correct lens ahead of time avoids the significant hassle and time wastage associated with the necessity of changing lenses in the field owing to an inappropriate FOV; something easily avoidable with proper preparation.

 

Next, you can identify a good starting point for each of the camera’s exposure settings: ISO, aperture and shutter speed. The specific settings you will settle upon once you’re in the field will undoubtedly change; the estimated initial values nonetheless reduce the number of decisions you need to make when you’re setting up in the dark with many other distractions likely competing for your attention. Equipped with the likely lens and aperture combination suitable for your nightscape image, one final parameter to check is the near-focus distance of the chosen lens and aperture combination.

This will be the case either with a focus distance of infinity or through hyperfocal focusing. You will recall that the near-focus distance dictates the closest distance an object can be from the camera and still remain in focus. If, however, part of the foreground is still too close to the lens despite your best efforts, all is not lost.

 

 

Developing the Landscape Astrophotography Workflow and Plan.

 

The culminating stage of our planning process is to summarize our ideas in the form of a worksheet and overall schedule for the astrophotography session. This schedule will include a time estimate for all the images we wish to acquire. This is extremely important since many of the images and image sequences can consume a surprising amount of time. For example, a multi-image Milky Way panorama comprised of twelve 2-minute apiece exposures will take approximately one-half hour. And that’s just for one (really good!) image.

 

A single star trail image can take 4 or 5 hours! Furthermore, you may wish to change lenses midway through your shooting session; something that is best kept to an absolute minimum when you’re in the field. Finally, different images may necessitate specialized equipment that you will want to ensure you have before heading into the field for the night, such as intervalometers, panoramic heads, lens filters, tracking heads, and so on. Clearly, scheduling and prioritizing the sequence of what images to take with which lenses, is critical.

 

 

Essential Software and Apps.

 

Today’s landscape astrophotographers are fortunate to have access to a large and ever increasing variety of sophisticated, free, or low cost software and apps specially tailored to their needs. These tools have revolutionized landscape astrophotography, especially when used on mobile devices.

 

For example, it is now possible to pinpoint the precise location, within a few feet in the field where you should assemble your camera and tripod to capture the full moon rising directly over a distant landmark hours, or even days, before the actual event! The tools listed here are simply representative of the types of tools you may find helpful. The ones that are described here are ones that I have personally used at home and in the field on many occasions.

 

 

Astronomy.

 

Astronomy software programs and apps allow you to explore the night skies in virtual reality for any date, past, present, or future. Many are freely available and have an extraordinary level of detail. They generally include clickable objects linked to further information or databases. Many apps include an augmented reality capability for use on mobile devices, where the app will display the night sky view corresponding to the orientation of the mobile device.

 

These simulation programs are valuable for many reasons. First, they allow you to gain an appreciation of the visible objects during different times of the year. You can search for specific objects to determine the best times to observe them. They allow you to simulate the movement of objects in the night sky, so you can quickly gain an appreciation of the direction of their motion and how it depends on azimuth and altitude.

 

Many have built in databases for the orbital trajectories of the International Space Station and major satellites. Two popular simulation programs for desktop or laptop systems are Stellarium and Starry Night.

 

 

You can find the reviews and the best price here on Amazon.

You can also download Stellarium here https://stellarium.org/

 

 

Both allow you to create a virtual planetarium and explore the night sky in detail. You can determine what objects are visible in the night sky for any place on Earth. You can estimate the field of view (FOV) necessary to photograph the objects of interest, allowing you choose the appropriate lens. Both programs allow you to simulate the passage of time in order to assess how the night sky objects move during the night, as well as over the course of days, months, and even years!

 

Having this knowledge before you venture into the field can save you immeasurable amounts of time, energy and frustration. Also, there is something almost magical about watching night sky objects emerge from twilight precisely as predicted. There are a number of apps for mobile devices that function in an equivalent manner. In addition to Stellarium, the ones that I use most frequently are Distant Suns and Star Walk. Both use the local coordinates of the user obtained from the GPS sensors of the device to calibrate the current view of the night sky. All also give you the option of manually entering an observing position anywhere on Earth to assess how the view of the night sky will appear from that location.

 

This feature is very useful for exploring the appearances of the night skies while planning a trip to distant locations. Finally, you have the option of setting a “Night Vision” mode, in which the mobile device screen is lit with red light, to help protect your night vision, instead of its normal bluish tints.

 

As an example, we might begin our session by opening the app, confirming the correct location, and then scrolling around the horizon and zenith to see what night sky objects will be visible that evening at different times. We might visit the southern or northern horizons to view the Milky Way and determine its azimuth at different times of night.

 

As we have seen for both sky-priority and foreground-priority images, we are often interested in determining the times when the Milky Way is positioned at a specific azimuth or with a certain orientation. We might also change the date and/or location to explore their effects. Finally, the PhotoPills (PP) and The Photographer’s Ephemeris (TPE) apps both deserve mention in this section owing to their wealth of astronomical data, including a moon phase calendar. Making these assessments before heading into the field saves time and allows you to position yourself in prime locations.

 

 

Photography—Processing Tools.

 

By far the dominant software for image post processing are Adobe Photoshop and Adobe Lightroom.  You can find Adobe Photoshop Elements for a good price here on Amazon. Also you can get one years subscription of Adobe Photoshop Lightroom CC plan Subscription also on Amazon here.

 

The fundamental reason both programs have gained such widespread use is their inherent ability to allow you to make non-destructive editing adjustments to your images without permanently affecting the original image. Many other software tools, or “plug-ins,” have been developed to perform specialized functions within Photoshop and Lightroom that is beyond the scope of this guide but you can read in detail about on the web. We have tracked down the price and reviews here on Amazon, Adobe Photoshop Lightroom CC plan | 1 Year Subscription

 

 

General Field Gear.

 

There are two items I never leave behind whenever I venture into the field for a nightscape photo session:

 

a reliable headlamp equipped with a red light setting, and,
a compass.

 

No other pieces of equipment are so important to your personal safety. If you’ve never used a headlamp, you’ll be astonished at how useful they are— both hands are kept free and the light always shines right where you’re looking. In fact, you should always carry a spare!

 

You may also want to bring a second hand-held flashlight as well. It is helpful for lighting the trail, light-painting projects, and a myriad of other tasks. Finally, don’t forget duplicate sets of spare batteries. A great idea is have a spare crank powered flashlight, I have a Solar & Hand crank powered flashlight no batteries needed. A no battery flashlight is perfect for emergencies. And I am surprised how cheap you can by it. you can find it on Amazon here it is the, Thorfire Solar Flashlight

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A compass is invaluable at getting oriented in new surroundings. I frequently use mine during the day to estimate the future locations of night sky objects, thus narrowing down choices of scene composition. Be sure to choose one that allows you to correct for the difference between true and magnetic north, or the magnetic declination. A magnetic declination adjustment is helpful since the earth’s magnetic North Pole is offset slightly from its physical North Pole.

 

Such models are often described as orienteering compasses. Correcting your compass for magnetic declination allows you to take readings directly from its dial while allowing the compass needle to point to magnetic north.

 

Your cellphone can also be invaluable in the field, even without coverage. Used with the apps described above, it can provide times of sunset/sunrise, moonset/moonrise and twilights, photography settings, as well as the positions and orientations of sky objects. A small, rechargeable power supply can be a helpful accessory if its power runs low. Finally, it may be able to summon emergency services, although coverage in remote areas is unreliable and often nonexistent.

 

Another vital device to carry into the field is a dedicated GPS device. Most of the time it’s not needed, but it can make an enormous difference if you become lost. Such devices are also invaluable at navigating in areas with limited coverage by cellphones, and have the added benefit of providing precise position coordinates for pinpointing your position.

 

Many models feature a “go-to” capability, which allows you to navigate to a specific destination, for example, your car, or camp at the end of the session. I have relied on this feature on several occasions to return from a nightscape session in dark, featureless surroundings. A roll of gaffer’s tape—photographer’s “duct tape” is a surprisingly useful accessory to keep in your camera bag. There are innumerable uses for it, from securing loose cables, to serving as a shim for a loose lens cap, taping handwarmers to your camera – you will be glad you brought it along.

 

A simple chair has the ability to transform an evening of nightscape photography from a battle of endurance to a relaxing night in the outdoors. Backpack chairs are perfect for carrying equipment and supplies a short distance, and also help whenever a brief (or long!) nap is needed. A dedicated camera backpack, however, is your best option for longer hikes.

 

Camera backpacks typically have myriad padded and zippered compartments for all your gear along with a carrying pouch for your tripod. You can use them to carry a surprising amount of gear quite a long distance. In cold-weather destinations, any of the available handwarmers are a wonderful way to stave off chilly, damp night air. They can also be used to keep your camera and batteries warm either by taping them in place with gaffer’s tape, attaching them via rubber bands, or even elasticized bandage wraps. Attached to your lens body, they can also help avoid dew formation and frost.

 

There are several miscellaneous items that are worth considering. I often keep a few energy bars, trail mix, or pieces of fruit inside my bag for a late night energy boost. A thermos of hot chocolate, tea, or coffee can also make a world of difference.

 

I generally keep a fleece hat, gloves, nylon windbreaker, and a bandanna on hand in case temperatures drop unexpectedly. You may wish to create a dedicated waterproof bag of sunscreen, insect repellent, and antibacterial disposable hand wipes; you never know when annoying insects can suddenly materialize and cause mischief. Earplugs and a headscarf or bandanna are also great at keeping insects and cool breezes at bay.

 

I always keep a small roll of toilet paper and a backpacking hand shovel tucked inside my bag in case a restroom isn’t nearby, and I’m on suitable public land. Finally, in bear habitat, a can of bear spray is good insurance. While this guide is no substitute for a complete course in bear safety, good bear-safety habits are vital for the bear’s health, as well as your own, and must be adopted whenever you travel in bear country, especially areas inhabited by North American grizzly bears.

 

 

Astronomy gear.

 

I always carry a planisphere with me when I venture into the night, preferably one with glow-in-the-dark markings.  You can find the one I have from Amazon is here.  Not only does it allow me to readily confirm the identity of specific objects, it helps in understanding how they move throughout the night. I also carry a green laser pointer (5 mW or less) to help in identifying night sky objects to others.

 

Photography gear.

 

The absolute necessities are your camera, tripod, memory cards, and batteries. It is a good practice to confirm that your camera actually contains its memory card and battery before leaving for your destination. While it may seem obvious, on more than one occasion, I have hiked into a pre-dawn location only to find an empty memory card slot in my camera and no spare memory cards in my pack—I had simply overlooked them and failed to check! Other essential gear includes a remote shutter release or an intervalometer, a color correction tool, a flashlight for light painting, a handheld loupe to assist in focusing on the stars, and a dust blower to keep the lenses clean.

 

Beyond these basics, I will occasionally bring along assorted filters, a panoramic head, a flash, and wireless remote triggers. If I intend to perform very long exposure star trails, I will bring the external battery pack for the camera and/or an external camera power supply. Small patches of Velcro and tabs attached to the upper legs of my tripod can help keep the intervalometer and other cables in order and untangled.

 

 

Five best astrophotography targets and how to capture them.

 

Aurora Borealis/Australis.

 

LENS (MM): Fisheye, 14–50
START: Late astronomical twilight to full darkness
ISO: 1600–12800
END: Early astronomical twilight (predawn)
APERTURE: sharpest
SHUTTER (SEC): Adjust as needed
COMMENT: Keep shutter speed low to retain structure.

 

 

Blue Hour.

 

LENS (MM): All
START: Evening – End of sunset; Morning – Beginning of astronomical twilight
ISO: Low (100–500)
END: Evening- End of astronomical twilight; Morning- Beginning of sunrise
APERTURE: Sharpest (minimum + 2 stops)
SHUTTER (SEC): Adjust as needed
COMMENT: Easy image to make; good silhouette opportunity.

 

 

Cityscapes.

 

LENS (MM): All; generally wide-angle
START: Golden hour (sunset)
ISO: 100–1600
END: Golden hour (sunrise)
APERTURE: Sharpest (minimum + 2 stops)
SHUTTER (SEC): Adjust as needed
COMMENT Good FLW filter opportunity during civil/nautical twilight

 

 

Constellations.

 

LENS (MM): Fisheye, 14–35
START: Mid-astronomical twilight (postsunset)
ISO: 1600–12800
END: Mid-astronomical twilight (predawn)
APERTURE: Minimum— sharpest
SHUTTER (SEC): Focal length (mm)/ 500
COMMENT: Good fog filter opportunity

 

 

Lunar Eclipse.

 

LENS (MM): 24 mm and higher
START: Mid-civil twilight (postsunset)
ISO: 100–1600
END: Mid-civil twilight (predawn)
APERTURE: Sharpest (minimum + 2 stops)
SHUTTER (SEC): Adjust as needed
COMMENT: Requires planning

 

 

Related questions.

 

 

What is astrophotography used for?

 

Astrophotography is photography of astronomical objects, celestial events, and areas of the night sky. Today, astrophotography is mostly a sub-discipline in amateur astronomy, usually seeking aesthetically pleasing images rather than scientific data. Amateurs use a wide range of special equipment and techniques.

 

 

How do you capture photos through a telescope?

 

The most inexpensive method of taking photographs through a telescope is called afocal. This means that you focus the telescope on the object you want to photograph and then point your camera into the eyepiece to take the photo. This method works well for point and shoot cameras and cell phones.

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